Circuit interrupter



June 18, 1940.

E. K. CLARK RCUIT IHIERRUPTER 'Filed April 21, 193s 3 Sheets-Sheet l D/Lrp/abemen /ff biches.

June 1s, 1940. E. K. CLARK 2,205,240

crncun' Iu'rannurrnn Filed April 21...1S38 y 3 Sheets-Sheet 3 WITNESSES: l lNV-ENTOR Patented June 18, 1940 PATENT OFFICE CIRCUIT INTEBRUPTER Earl K. Clark, Mansfield, Ohio, assigner to Westinghouse Electric & Manufacturing Company,

East Pittsburgh, Pa., vania a corporation of Pennsyl- Application April 21, 1938, Serial No. 203,317

13 Claims.

My invention relates to-circuit interrupters, and more particularly, to thermally controlled, manually operable snap-acting switches.

An object of my invention is to provide an inexpensive, ruggedly constructed,v conveniently operable two-pole direct-current snap-acting switch which incorporates a safety cut-off thermostat with an inexpensive, compact, manually operable snap-acting switching device.

A further object of my invention is to provide a thermally actuated, manually reset, snap-acting switch incorporating a bimetallic member which will, after its operation, be free to return to a normal operative position without restraint l5 and without changing the operative position of the contact means associated therewith.

A further object of my invention is to provide a two-pole direct-current snap-acting switch which is manually operable in either direction and has incorporated therewith a thermally responsive device for tripping the contact means.

A further object of my invention is to provide a thermally-actuable manually-operable snapacting switch which includes an operating resilient member retained in a double elastic curve for decreasingly resisting the movements of an operatively associated movable Contact through part of its travel and increasingly assisting it through the balance of its travel.

A still further object of my invention is to provide a thermally-actuable manually-operable snap-acting switch in which the cooperating contacts thereof cannot be manually reengaged While the thermally-actuating device therefor remains in an open or hot position.

A further object of my invention is to provide a ythermally-actuated, manually-operable, snapacting switch having a self-contained device for indicating the position of the switch.

Other objects of my invention will either be pointed out specifically in the course of the following description of a device embodying my invention, or will be apparent from such description. In the accompanying drawings: Figure 1 is a top plan view of the device embodying my invention; v

Fig. 2 is a bottom view of the device shown in Fig. 1;

Fig. 3 is a curve chart graphically illustrating the operation of the device embodying my invention;

Fig. 4 isa sectional view taken along the line IV-IV of Fig. 1, showing the device in its operative position;

' cooperating contacts Fig. 5 is a view similar to Fig. 4 showing the device in its inoperative position;

Figs. 6 and 'I are sectional views similar to Fig.

5, illustrating modied forms of the device embodying my invention; and 6 Fig. 8 is a sectional viewsimilar to Fig. 6 showing a modied manner of mounting the operating handle.

Referring to the accompanying drawings, I show a Athermostat I0 including a supporting 10 structure I2, cooperating movable contacts I4 and stationary contacts I6, operating stem I8, elastic overcenter spring 20, operating handle 22, coiled actuating spring 24 and a bimetallic heatresponsive device A26. 15

As hereinafter described in greater detail, the I4 and I6 are operatively associated with the operating handle 22, through operating stem I8 and coiled spring 24. In addition, the stem I8 is suspended at its lower end on 20 the elastic overcenter spring 20, in such a manner that the spring 20 will produce a snap-acting movement oi' the stem I8 and movable contacts I4 along the longitudinal axis of stem I8. The manual operating lever 22, through the move- 25 ments thereof and through the cooperative action of spring 24 and resilient member 20, effects engagement or disengagement of the cooperative contacts I4 and I6 with a snap-acting action independent of the movement of bimetallic disc 26. However, the bimetallic disc 26, including an impact pin or impeller 28, is operatively associated with the operating stern I3 and resilient member 20 so that the disc 26 will effect movement of stem I8 and open the cooperating contacts at a SI5 predetermined temperature value. As there is no direct connection between the stem I8 and disc 26, the disc 26 and impeller 23 return to their original or cold position without restraint and the cooperating contacts I4 and I6 can only be 40 reengaged by means of the manual operation of operating handle 22.

More specifically, the supporting structure I2 includes, in this instance, an insulating base support 30 and a frame 32 comprising` an irregularly 45 U-shaped strip. The frame 32 is rigidly attached to the base 30 by means of screws 34. However, it is to be understood that if it be desired, the supporting structure I2 may be formed of a single member, or in any other suitable manner. 5o

The movable contacts I4 include a movable contact plate 36 and a plurality of contact members 38 which are insulatedly attached to the movable contact plate 36 by means of the rivets 40 and insulating washer 4I. It is preferred that 55 the contacts 38 be loosely mounted with respect to the contact plate 38 and the cooper-ating stationary contacts l so as to produce a satisfactory electrical contact therewith. The stationary contacts l@ include, in this inst-ance, a plurality of metallic arcuate plates 42 which are directly attached to the insulating base 30 by means of suitable rivets 44. The movable contact members Sil coopera-te with the stationary con tacts so as to bridge the gaps between the arcuate stationary contact plates 42 in a manner well known to the art.

rhe movable contact plate 3E is adjustably and swivel-connected to the upper end or" the operating stem i8 by means of thc swivel connection Lili, which has a threaded engagement with the stem i8. This connection permits the movable Contact plate 36 to be adjustably positioned along the longitudinal axis of the operating stem ld for a reason hereinafter explained. A lock nut may also be positioned upon the upper end of the stem I3 so as to lock the swivel connection il@ in the desired position. This ensures permanent operating adjustment o1" the switch throughout the life thereof.

The operating stein I3 is centrally and slidably inserted through the stationary base 3U, as shown in Figs-4 and 5. This permits the stern to move freely along its longitudinal axis and substantially normal to the base 3B, ensuring the proper engagement of the cooperating contacts id and A shoulder or ange 5S is positioned intermediate the ends of stein i8 to permit cooperative action with the coiled actuating spring J 2d, in a `manner and for a purpose hereinafter described. In addition, the stem i5 is suspended on, or rigidly attached at its lower end to substantially the center of the elastic over-center spring as hereinafter described. ri'his spring suspension of the stem i3 is entirely frictionless and may, therefore, be precisely adjusted to produce an exact over-center snapping point and vertical biasing component of the resilient member as hereinafter described.

The elastic over-center spring 2e is of the flat or strip type and is rigidly attached, at substantially the ends thereof, to the frame 32 by means of rivets 52 and and to the operating stem t3 intermediate the ends thereof by means of lead and follow nuts 54 threaded upon such stem. The resilient over-center member 20 is held in an inherently unstable or compound form of curvature by means of the adjustably rigid connection between the stem I8 and substantially the central portion thereof. However, due to the rigid connection between stem I8 and resilient member 20, this inherently unstable form of curvature is actually maintained in a stable condition. The resilient member 20 is, therefore, forced to assume and retain a double elastic curve, substantially as shown in Figs. 4 and 5.

Because of this double elastic curvature resulting in an over-center action, the resilient member 2li will produce a snap-acting action of the stem I8 and cooperating movable contacts I4 to either an open or closed position, as hereinafter described.

The resilient member 2D, while being restrained in its double elastic curvature, nevertheless attempts to assume one of its stable or simple elastic curves, substantially as shown by the dotted lines 58 in Fig. 4. This inherent action of resilient member 20 produces a vertical biasing component on the stem I8. This vertical biasing component decreasingly resists the movement of stem I8 from one operative position until the central portion of the resilient member reaches and passes the neutral (in this instance, substantially a line joining the rivets 52 and 53), whereupon the resilient member hen increasingly aids the travel of stem I8 until it reaches its second operative position. This inherent characteristic of. resilient member 2U produces by impact of pin 28 a snap action of stem I8 in either direction, as more fully explained and described in my copending application Serial No. 198,077, led March 25, 1938, and assigned to Westinghouse Electric Si Manufacturing Company.

The operating handle 22, in this instance, is of channel shape ind extends through an aperture 58 in one side of the frame 32 and is hingedly attached to the opposite side of such irame by means of a suitable hinge-pin ED. It being preferred that the handle 22 be hingeably attached to the frame 32 at a vpoint opposite to that from the aperture 58, substantially as shown in Figs. 4 and 6. However, if desired, the handle 22 may be hingeably attached to the frame 32 adjacent the aperture 58 by means of a bracket 80, substantially as shown in Fig. 8 and as hereinafter described.

The operating handle 22, in the preferred construction thereof, has an aperture 23 positioned in its upper face intermediate the ends thereof so that the operating stem I8 may freely extend therethrough. This permits the handle 22 to be moved with respect to the stem I8 without any binding action therewith. The operating handle 22 extends outside the frame 32 and supporting structure I2, where a suitable operating knob E4 is positioned upon the free end thereof.

The coiled actuating spring 24 is of the compression type and is positioned about the operating stem I8 between, although not contacting, the shoulder 5U thereof and the operating handie 22, substantially as shown in Figs. 4, 5, 6, 7 and 8. Flat washers 62 and 63 are preferably positioned about the stem I8, one below the spring 24. The washer 62, positioned above the spring 24, due to its cooperation with shoulder 50 on stem I8, limits the longitudinal movement of the upper end of spring 24, or that end farthest from the operating handle 22, with :a

respect to the operating stem I8. In other words, due to the presence of washer 62, the upper end of spring 24 will undergo no longitudinal movement, except as the stem I8 moves,

at which time the spring will move therewith.

The washer 63, positioned below the spring 24, is operatively associated with the handle 22, whereby the upward movement of handle 22 may be readily transmitted to the spring 24 and the spring will follow the downward movement as hereinafter described.

The bimetallic heat-responsive device 26 is, in this instance, a bimetallic disc of a familiar type, rim mounted to the frame 32 by means of annularly grooved pins 66. The pins 66 are rigidly attached to a supporting plate G8, mounted on frame 32 in this instance by being welded thereto, as shown at 69 in Figs. 1, 2, 6, 7 and 8, so as to permit ready access to the disc 26 without removing it from the supporting frame 32. However, it is to be understood that if desired, the disc 26 could be mounted on an extension of frame 32, or in any other suitable manner.

The impact pin 28 is adjustably attached to the central portion of the disc 26 and will move in a above and one vertical direction as the central portion of the bimetallic disc flexes from one position to another in response to temperature changes. The impact -pin 28 is adjustably and swlvelly or loosely attached to the central portion of the bimetallic disc 26 by means of nuts 14 cooperating with shoulder washer 16. rlhe impact pin 28 extends upwardly from the disc 26 through aperture 12 in the supporting plate 68; and the head 18 thereof, preferably hexagonal in shape, is positioned within a suitable similarly shaped aperture 18 (to` prevent turning of head 18) located in the bottom portion of the supporting frame 32.

With the impact pin head 18 and disc 26 being mounted free from stem I8 land cooperating contacts I4 and I6, it is obvious that the head.

18 of impact -pin 28 and disc 26 may, therefore, move vertically with respect to the frame 32, stem I8 and cooperating contacts I4 and I6 a predetermined distance without causing any movement of stem I8 and contacts I4 and I6. The amount of this movement in this instance is B, as shown in Figs. 3 and 4.

With the bimetallic disc rim mounted, as shown, the central portion thereof will flex from a concave position (low temperature) to a convex position (high temperature) substantially as shown in Figs. 4 and 5, respectively. Accordingly, by adjusting the relative position of the head 18 of impact pin 28 with respect to the central portion of the bimetallic disc 26, the tripping or operating temperature at which the bimetallic member 2,6 will function may be readily adjusted. it, therefore, follows that the tripping or operating temperature of the contacts I4 and I6 will be adjusted in accordance with such adjustment of the thermostat.

ln thermally operating or tripping the device embodying my invention, it isA assumed that the bimetallic disc 26 be operatively associated with a suitably heated device or body (not shown) in a well known manner, whereby the switch I8 will respond to the temperature thereof. As the temperature of disc 26 increases to a predetermined value, the bimetallic disc 26 will flex from an operative position, as shown in Fig. 4, to an inoperative position, as shown in Fig. 5. As the disc flexes from its operative to its inoperative position, that is, the open and closed positions, respectively, of the switch, theimpact pin 28, rigidly attached thereto, will likewise be moved substantially normal to the plane of the disc, or in this instance, along the axis of 'the operating stem I8.

As the impact pin 28 is moved vertically, in this instance the distance B, before the impact pin 28 strikes stem I8, such disc and-impact pin will acquire a certain amount of kinetic energy, which in addition to the flexing energy of the bimetallic disc 26, will, upon the occurrence of such impact, cause the operating stem I8 and cooperative resilient over-center device 28' and movable contacts I4 to be moved vertically with a snap-acting action. The combined kinetic energy and flexing energy will move the stem I8 a distance A before the central portion of the resilient member 28 reaches its neutral. -During the travel of stem I8 through the distance A, the resilient member 28 decreasingly resists the movement thereof. This decreasing resistance of member 28 aids in producing an accelerating movement of stem I8 and cooperative contacts I4 which causes the stem I8 to be carried beyond the neutral. As the stern I8 is carried beyond the neutral the resilient member 28 then increasingly aids the continued movement' of stem I8. ThisV cooperative action of disc 26 and resilient member 28, will substantially instantly accelerate the stem I8 and movable contact I4. Accordingly, it is obvious that the bimetallic disc, while being independent of the stem I8, resilient member 28 and cooperating contacts I4 and I6, effects separation or disengagement of contacts I4 and I6, as the bimetallic disc 26 flexes from its concave to its convex position with a snap action.

When the movable parts (contacts I4, stem I8, resilient member 28 and handle 22) of the switch I8 come to rest, the lower end of stemv I8 will again be separated from the impact pin 28 since movement of the central portion of spring 28 is greater than movement of disc 26, and the movable contact I4 will be positioned above the stationary contact I6, substantially as shown in Fig. 5. In addition, the central portion of the resilient member 28 will be a considerable distance above its neutral plane, as shown by C in Figs. 3 and 5.

inasmuch as the bimetallic disc 26 and operatively associated impact pin 28 are not in any way connected with the impact stem I8, resilient member 28 of the cooperating contacts I4-I6, it is apparent that such bimetallic member is free, upon cooling, to return to its normal concave position Without any restraint. Accordingly, as the heated body cools to a predetermined value, the disc 26 and impact pin 28 automatically return to their original operative position, as shown in Fig. 4. This in turn permits the movable contacts I4 to be manually reengaged with the stationary contacts I6 by means of operating lever 22, as hereinafter described.

When it is desired to have the cooperating contacts l4-I6 reengaged, it is merely necessary to have an operator manually apply a downward pressure upon the knob 64 of operating handle 22. This pressure will be transmitted through handle 22 to the stem I8 and resilient member 28, which will result in the stem I8 and the movable contacts I4 being moved downwardly. As the manually applied pressure becomes greater than the restraining action of resilient member 2U, the stem I8 will be started in its downward travel. Inasmuch as the resilient member 28 again decreasingly resists the application of an external force until it reaches its neutral position and then increasingly aids the downward movement, it is apparent that such external manually applied pressure or force will,

through the cooperating action of resilient member 28, cause the-stem I8 and contacts I4 to be moved downwardly with an accelerating or snapaction. In addition, the inherent character of resilient member 28 produces and ensures a positive contact pressure between contacts I4 and I6. This contact pressure is represented by F in Fig. 3.

Should it befdesired to manually disengage the cooperating contacts I4 and I6, even though the thermally operating or tripping device remain in an operative position, the operating handle 22 is manually actuated upwardly by means of knob 64. The upward travel of operating handle 22 will then act upon the coiled spring member 24 through the washer 63. However, inasmuch as coiled spring member 24 has a greater deection per unit of pressure than the biasing action of the elastic over-center spring 28, such coil spring 24 will be compressed with the upward movement of the handle 22 until the pressure therein is equal to and greater than the restraining action of the resilient member 20. This restraining action is equal to the contact pressure F. When the pressure applied to stem I8, through spring 2t, becomes greater than the restraining action or" resilient member 20, such pressure will cause the stem I8 and cooperative movable contacts M to be moved vertically along its longitudinal axis, rst, against the decreasingly restraining action and then being assisted by the increasingly aiding action oi the resilient member 28. Due to this inherent character of resilient member 28 which decreasingly resists the action of coil spring 24 until resilient member 28 reaches its neutral, after which it increasingly aids the travel of stem i8, such stem I8 and contacts will be moved upwardly with a snapaction.

It is, therefore, obvious that the manually movable switch lever 22 may readily operate the cooperating contacts i4 and i8 whenever it be desired, with a snap-acting action to either an operative or inoperative position. In addition, it is obvious that, inasmuch as there is no connection between the bimetallic disc and the stem i8, the cooperating contacts i4 and I6 can only be manually reengaged. However, it is liliewise obvious that the cooperating contacts M and it may be either manually or thermally disengaged with a snap-action.

in addition, it is apparent that the exposed portion of the operating handle 22, or say, knob functions in an additional manner as a selfcontained device which indicates the actual position of the cooperating contacts i4 and I6.

As a modied form of construction, the operating lever 22 may be hinged to the supporting trame 82 by means of a bracket 88 which is rigidly attached to such frame substantially as shown in Fig. 8. The bracket 8U is rigidly attached to the frame 32 adjacent the aperture 58 through which the handle 22 extends. The handle 22 may then be rotated about the hinge pin iii operatively associated with bracket 8D. Vv'ith the operating handle 22 hingedly mounted to the frame 32 in such a manner, the inner end Si thereof may be operatively associated with the stem i8 without the need of being extended beyondv such stem. The inner end 8l of handle 22 is operatively associated with the stem I8 by means of washer 63 and follow nuts 54 substantially as hereinabove described. Accordingly, it is apparent that a switch constructed in such a manner will operate substantially as hereinabove described. E-Iowever, the direction of operation or" the handle 22 is opposite to that shown in Fig. e.

If it is desired to have the switch I8 constructed in such a manner that it will be impossible to manually reengage the cooperating contacts lil and I8 until the bimetallic disc 26 is in its original cold or normal concave position, an additional resilient member 82 may be positioned intermediate the operating handle 22 and the follow nuts 54, as shown in Fig. 7.

The resilient member or flat spring 82 is rigidly attached at one end thereof to the operating handle 22 intermediate the stem i8 and knob le, by means of a rivet 83. The other end thereof is operatively associated with stem i8 and resilient member 20 by resting upon follow nuts 54, as shown in Fig. 7.

An adjustable screw 84, which is threadedly attached to frame 32, limits the downward movement of the operating handle 22. The screw 8l, in this instance, is threaded through a protruding portion 85 of the frame 32 so as to permit ready adjustment. A lock nut 86 is associated with screw 84 to lock it in the desired position.

The resilient member 82 should be of such character that it will apply a downward biasing pressure upon follow nuts 54 and stem I8 with a downward movement of handle 22. This biasing pressure of member 82 should be greater than the upward restraining action of resilient member 20, and must be less than the upward biasing action of bimetallic member 26 at its opening temperature. This differential pressure between members 82 and 2U will tend to slightly raise the closing temperature of the birnetal. However, when the manually applied downward pressure on handle 22 is released the upward biasing action of resilient member 2U if it was not originally biased beyond the neutral, will cause the stem i8 and handle 20 to return to their normal positions)q It is to be understood that even should the resilient member 20 be biased beyond the neutral, the upward biasing action of resilient member B2 upon handle 22 would cause such handle and stem i8 to return to their normal open position. The only time that resilient member 20 would be biased beyond the neutral would be when disc 26 has changed its curvature due to creepage occurring during cooling of the disc. At such time the distance below neutral, corresponding to D in Fig. 6, would be exceedingly small.

Accordingly, with the resilient member 82 positioned intermediate the operating handle 22 and resilient member 28, the operating lever 22 may be moved downwardly without causing the immediate movement of resilient member 20. Due to the action of resilient member 82, the stem I8 and resilient member 20 may be moved towards the disc 26 with the movement of handle 22. However', the force being applied through resilient members 20 and 82 is less than the oppositely acting force of the bimetallic disc 26, and, therefore, it is apparent that the operating handle 22 cannot reengage the contacts I4 and I6 until the disc 26 has exed to its original cold position, it being understood that stop-screw 84 has been adjusted so that the handle 22, through the action of resilient member 82, cannot overcome the restraining action of disc 26.

The spring 24 in this modification should be shortened so that when the handle is in its lower position, contacting stop-screw 84, as shown in Fig. 7, it just contacts the handle without being compressed. This permits handle 22 to operate stem I8 and resilient member 28 in a manner as hereinabove described, without nullifying any of the contact pressure produced by the resilient member 20 when the switch is in a closed or operative position.

It is, therefore, obvious that with resilient member 82 located intermediate the operating handle 22 and resilient member 20, such handle may be moved downwardly without imparting a corresponding downward movement to the stem I8 and its cooperating movable contacts I4. It is, therefore, obvious that with a switch embodying this feature, such switch will be capable of being manually and thermally opened, but manually closed only when the bimetallic tripping device thereof is substantially at or below its closing temperature and has moved to its normal or cold position.

Inasmuch as a main object of this modiiication is to limit the downward movement of the stem I8 and the central portion of the resilient member 20 with respect to the operating handle 22, it is apparent that this may be accomplished in an additional manner, merely by limiting the downward travel of handle 22, as shown in Fig. 6. This limiting of the downward travel of operating handle 22 may be accomplished by the proper adjustment of stop-screw 84. The stopscrew 84 may be adjusted so that the amount of downward travel of stem I8, as handle 22 is actuated downwardly, will be slightly below the neutral, as shown by D lin Fig. 6. However, due to the adjustment of stop-screw, the downward movement of stem I8, through the action of handle 22, cannot force the disc 26 to return to its normally closed position.

Inasmuch as the distance D, or that distance which the central portion of resilient member 20 is below the neutral, is very small, the resilient member 20 will exert a correspondingly small downward pressure upon disc 26. This in turn will tend to cause the closing temperature of the bimetal to be slightly raised. However, this tendency will be exceedingly small and will not seriously interfere with the calibration of the switch.

In the absence of resilient member 32 the stem i8 will remain in a lowered or reset position. Accordingly, the contacts will be reengaged with a snap action as the disc 26 snaps to an operative position.

lt is, therefore, obvious that a switch embodying my invention may be either thermally or manually opened, thermally reclosed after manual resetting, cr manually closed, either dependent on or independent of the position of the thermostat, with all contactactions being snapacting.

Various further modifications may be made in the device embodying my invention without departing from the spirit and scope thereof, and I desire, therefore, that only such limitations shall be placed thereon as are imposed by the prior art and the appended claims.

I claim as my invention:

1.. A circuit interrupter including, in combination, a supporting structure, a plurality of cooperating contacts, at least one of said contacts being movable, a movable operating stem associated therewith, resilient means biased by said stem into a double elastic curve for causing movement of the stem and associated movable contact to open and closed positions, and means independent of the resilient means andi stem for actuating the resilient means.

2. A circuit interrupter including, in combination, a supporting structure, a plurality of cooperating contacts, at least one of said contacts being movable, a movable operating stem associated therewith, resilient means for causing movement of the stem and associated movable contact to open and closed positions, an operating handle movably attached to the supporting structure, operating means for said movable contact independent of the stem and resilient means, and means comprising the operating handle for actuating the resilient means.

3. A circuit interrupter including, in combination, a plurality of cooperating contacts, at least one of said contacts being movable, a movable operating stem associated therewith, resilient means for causing movement of the stem and associated movable contact to open and closed positions, a coiled spring operatively associated with the stem and resilient means, operating means for said movable contact independent of the Vresilient means and stem, and means comprising the coiled spring and the means independent of the resilient means and stem for actuating the resilient means.

4. A circuit interrupter including, in combination, a supporting structure, a plurality of cooperating contacts, at least one of said contacts being movable, an operating stem movable with said one contact, resilient means for causing movement of the stem and associated movable contact to open and closed positions, a bimetallic thermal-responsive device attached tov the supporting structure and independent of the stem, said device actuating the resilient means at a predetermined thermal value, and means independent of the device for manually actuating the resilient means.

5. A manually reclosable snap-acting switch including, in combination, a supporting structure, a plurality of cooperating contacts, a stem for movably operating one of said contacts, an elastic overcenter device rigidly attached to the structure and to the stem for causing a snap-acting mo'vement of the stem, an operating handle hingedly attached to the supporting structure and operatively assbciated with the elastic device, and means actuated by the handle for operating the stem and the movable contact.

6. A manually reclosable snap-acting switch including, in combination, a plurality of cooperating contacts, a stem for movably operating one of said contacts, an elastic overcenter device for causing a snap-acting movement of the stem, an operating handle operatively associated with the elastic device, and means actuated by the handle for operating the stern and the movable contact, said means including a resilient member interposed between the handle and the stem.

7. A manually reclosable snap-acting switch including, in combination, a plurality of cooperating contacts, a stem for movably operating one of said contacts, an elastic overcenter device for causing a snap-acting movement of the stem, an operating handle operatively associated with the elastic device, a coiled spring positioned about the stem and operatively associated at one end to the stem and to the operating handle at the other end, and`means including the actuation of the coiled spring by the operating handle for operating the stem and vthe movable contact.

8. In a circuit interrupter, a supporting structure, contact means, a movable stem operatively associated therewith, means for causing a snapacting movement of the stem, a thermal-responsive device adapted to change its shape upon the occurrence of a predetermined condition and while changing from its normal shape to actuate the movement of the stem, an operating handlev for operating the stem and contact means, a resilient member rigidly attached to the handle and associated with the snap-acting means, and means including the resilient member for preventing the reengagement of the contact means until the thermal-responsive device has returned to its normal position.

9. In a circuit interrupter, a supporting struclture, contact means including at least one movable contact, a movable stem operatively associated therewith, means for causing a snap-acting movement of the stem, a thermal-responsive device adapted to change its shape upon the occurrence of a predetermined condition and While changing from its normal shape to actuate the stein, an operating handle for operating the stem and movable contact, a stop-screw operatively associated with the supporting structure and operating handle, and means including the stopscreW for preventing the reengagement of the contact means until the thermal-responsive device has returned to its normal position.

l0. In a circuit interrupter, contact means movable between an open-circuit position and a closed-circuit position, means biasing said contact means toward whichever of said positions it is moved toward, means responsive to a predetermined condition for impacting said contact means to move it toward open-circuit position, and an actuating member operable for moving said contact means toward each of said positions but being incapable of moving said contact means to closed-circuit position when said means responsive to a predetermined condition is acting to move the contact means toward open-circuit position.

1l.. A snap-acting switch comprising a supporting structure, a plurality of cooperating contacts, means for carrying one of said contacts and movable along a given line, an elastic over-center device having a portion movable with said movable means for causing a snap-acting movement thereof, the elastic movement of said overcenter device being along said line, thermal-responsive means for actuating said movable means and elastic device along said line, and means independent of said thermal-responsive means operable on said elastic device in both directions to actuate the movable contact.

12. A snap-acting switch comprising a supporting structure, a plurality of cooperating contacts, movable means for carrying one of said contacts, an elastic overcenter device having a portion movable with said movable means for causing a snap-acting movement thereof, and thermal-responsive means normally out of engagement With said movable means for operating the same by impact.

13. A snap-acting switch comprising a supporting structure, a plurality of cooperating contacts, movable means for carrying one of said contacts, an elastic overcenter device having a portion movable with said movable means for causing a snap-acting movement thereof, thermal-responsive means normally out of engagement With said movable means for operating the same by impact, and means operable on said elastic device in both directions to actuate the movable contact.

EARL K. CLARK. 

